The present invention relates to an electromechanically operated disc brake for motor vehicles with a caliper as well as an actuating unit located on the caliper, and with two limitedly displaceable friction linings located in the caliper, each of which acts together with one side of a brake disc respectively, wherein one of the friction linings can be brought into engagement with the brake disc directly by the actuating unit via an actuating element and the other is brought into engagement with the brake disc through the effect of the reaction force generated by the caliper, and wherein the actuating unit exhibits an electric motor arranged coaxially to the actuating element as well as a reducing gear unit arranged between the electric motor and the actuating element, with the rotor of the electric motor being ring-shaped and radially disposed about the reducing gear unit.
This type of electromechanically operated disc brake is known from DE-A-195 11 287.3, for example. The actuating unit of the known disc brake consists of an electric motor, whose rotor drives a threaded nut by means of a roller screw drive element or a sun gear. The rotation of the threaded nut is transmitted to an actuator sleeve or causes its axial displacement, and this in turn causes the friction lining activated by the actuating unit to be brought into engagement with the brake disc. For this purpose, the rotor of the electric motor preferably is radially disposed about the roller screw drive element. Unfavorable features of the known electromechanically operated disc brake, in particular, are the relatively high consumption of electric power as well as considerable heating of the electric motor, which occur especially whenever high clamping forces have to be applied for a long period of time.
Hence, the object of the present invention is to propose an electromechanically operated disc brake of the type described above, which can maintain high clamping forces with very slight electric power after these have been applied. In addition, the heating of the electric motor is to be reduced to a minimum.